News and Perspectives from Pacific Gas and Electric Company

The grassroots climate activist organization 350.org owes its name to the number of parts per million (ppm) of carbon dioxide in the air that many scientists say represents a safe limit for humanity.

Reaching 400 ppm is a "sobering milestone," one researcher says.

So it should come as a shock that as early as next month the concentration of CO2 in the Earth’s atmosphere is set to surpass 400 ppm. Carbon dioxide is a potent greenhouse gas blamed by most climate scientists for heating the globe and causing increasingly disruptive weather extremes.

“The 400-ppm threshold is a sobering milestone, and should serve as a wake-up call for all of us to support clean energy technology and reduce emissions of greenhouse gases, before it’s too late for our children and grandchildren,” said Tim Lueker, a Scripps oceanographer.

The news comes from the Mauna Loa Observatory on the island of Hawaii, which has been documenting the steady rise in CO2 levels since 1958 as the world continues to burn carbon-rich fossil fuels for energy.

Steady for 800,000 years, then …

For the past 800,000 years, CO2 levels bounced around in a band between 200 ppm and 300 ppm. The jump to 400 ppm has all come since the start of the industrial revolution.

A team of scientists reported last year in Science magazine that you’d have to travel back at least 15 million years in a time machine to experience CO2 levels this high. You probably wouldn’t want to stay for long.

Back then, “global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,” said the paper’s lead author, Aradhna Tripati, an assistant professor in UCLA’s department of Earth and space sciences.

In a speech to Columbia University’s Center on Global Energy Policy this week, White House National Security Advisor Tom Donilon called the “transformation in the global climate” driven by the world’s use of fossil fuels “not just a transcendent challenge for the world but a present-day national security threat to the United States.”

At home, he noted, record warming contributed to extraordinary droughts, wildfires, and a slew of weather-related disasters last year. Abroad, similar stresses inflicted on weaker societies “will lead to new conflicts over refugees and resources; new suffering from drought and famine; catastrophic natural disasters; and the degradation of land across the globe.”

‘Transformation of the world’s energy economy’

Both threats, he said, “push us toward the same longer-term endpoint: the comprehensive transformation of the world’s energy economy toward cleaner, more sustainable energy solutions.”

Unfortunately, as the Mauna Loa data indicate, that transformation appears to be coming too slowly.

Close to home, the state of California is in the vanguard of change by implementing the California Global Warming Solutions Act. And PG&E, whose CO2 emissions rate is only about one-third the national average for utilities, is leading change by investing heavily in energy efficiency and clean energy.

But until the rest of the nation and the world follow suit, the concentration of greenhouse gases in the atmosphere will continue their dangerous climb.